Fluorescent MHC-peptide multimers, commonly referred to as tetramers are widely used to detect, enumerate, analyze and sort antigen-specific CD8+ T cells (1, 2). Monomeric MHC-peptide complexes are produced by refolding of a MHC heavy and light chain in the presence of a peptide of interest and subsequently are biotinylated at a C-terminally added biotinylation sequence peptide (BSP, LHHILDAQKMVWNHR, SEQ ID NO: 1) the biotin-transferase BirA. Fluorescent conjugates are obtained by reaction of biotinylated MHC-I-peptide monomers with phycoerythrin (PE) or allophycocyanine (APC) labeled streptavidin (2, 3). Although such reagents generally perform well, they have shortcomings: 1) they are heterogeneous in terms of stoichiometry and configuration, which compromises stringent binding analysis (4). 2) The enzymatic biotinylation is tedious, expensive and in the case of unstable MHC-peptide monomers causes degradation during the enzymatic reaction, which is performed at elevated temperatures (5). 3) For some studies antigen-specific CD8+ T cells are isolated by cell sorting (e.g. FACS or MACS). Conventional multimers stably bind to cells and induce strong T cell activation, which can induces death and result in loss of CD8+ T cells, questioning that the surviving cells are representative for the original populations (5-8). To overcome this, reversible multimer have been introduced, which contain low affinity biotin analogues and hence dissociate upon addition of free biotin. With these reagents significantly improved sorting and cloning efficiencies are obtained; however, they are costly and tend to be less stable (5, 8).